Tape drives typically store multiple tracks of data onto a tape simultaneously. For example, tape drive that use the linear tape open (LTO) specification may write 16 tracks of data onto the tape at the same time. Many tape drive are configured with read heads positioned adjacent to or behind the write heads. This allows the tape drive to read the data from the tape as it is being written onto the tape. This feature is typically called read-while-write. Using the read-while-write feature a tape drive can immediately detect errors written onto the tape.
When an error is detected using the read-while-write feature, the data can be re-written to a different location on the tape. Currently all 16 tracks of data are re-written onto the tape even when only one track of the original 16 tracks had errors.